Hypotheses: Suberythemogenic Narrowband UVB (NB-UVB) phototherapy is an effective outpatient treatment for moderate-to severe plaque type psoriasis in Caucasian and darkly pigmented patient populations. Specific Aims: 1. To study the efficacy of outpatient NB-UVB in the treatment of psoriasis in Caucasian and dark pigmented patients (a group of patients who historically have responded poorly to BB-UVB). 2. To compare results from a full body treatment to prior results using split body approach. 3. To document therapeutic effectiveness by analyzing biopsies from treated lesions using objective histopathological measures.